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Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

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Item 1.02

Termination of a Material Definitive Agreement.

On September 4, 2018, Agios Pharmaceuticals, Inc. (the Company) and Celgene Corporation (Celgene) agreed to terminate (i) the
collaboration and license agreement dated April 27, 2015 between the Company and Celgene and (ii) the collaboration and license agreement dated April 27, 2015 between the Companys wholly owned subsidiary Agios International Sarl and Celgene
International II Sarl, in each case effective as of September 4, 2018 (the AG-881 Agreement Termination Date). The Company and Celgene had established a joint worldwide collaboration focused on the development and commercialization of
products containing AG-881. From and after the AG-881 Agreement Termination Date, the Company will obtain sole global rights to AG-881 and no party will have a financial obligation to the other parties, including milestones, royalties or other
payments, except that (a) Celgene shall be eligible to receive royalties from the Company at a low single-digit percentage rate on worldwide net sales of products containing AG-881 and (b) the Company and Celgene shall split certain agreed-upon
worldwide development costs for AG-881 until December 31, 2018. In addition, for a specified period and subject to specified exceptions, Celgene and its affiliates shall be prohibited from developing, manufacturing or commercializing any product
that inhibits isocitrate dehydrogenase 1 at specified levels of binding for any indication and the Company shall be prohibited from developing, manufacturing or commercializing AG-881 in hematologic indications.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by
the undersigned hereunto duly authorized.